Molecular Cloning and Characterization of Peroxidase from Haloferax volcanii

Lignocellulosic biomass requires pre-treatment because of its phenolic lignin components which form cross-linkage with cellulose and hemicellulose of biomass and hinder biofuel conversion. Pre-treatment of biomass with ligninolytic enzymes is an eco-friendly and low-energy input alternative method. Haloferax volcanii is a halophilic archaeon that thrives in hypersaline conditions and produces highly stable enzymes that may be useful for oxidizing complex phenolic compounds. Here, the H. volcanii katG ( hvo_1778 ) encoding peroxidase (EC:1.11.1.21) was overexpressed and characterized for its activity with 2.38 (U/mL) of volumetric enzyme activity and 3.77(U/mg) of specific enzyme activity at 15 mM of H 2 O 2 . Strains overexpressing katG gene from a constitutive ribosomal RNA P2 promoter were found to produce increased peroxidase activity which is based on catalysing the H 2 O 2 -dependent oxidation of veratryl alcohol, a natural substrate of lignin peroxidases. The lignin peroxidase assay shows that the H. volcanii katG overexpression strains with a maximal activity of 12.2 U/mL and specific activity of 19.35 U/mg. The isolated protein showed bands approximately at 80 and 100 kDa respectively. The digestion of Erianthus biomass with peroxidase enzyme was performed and visualized using scanning electron microscope. It showed holes, potholes as a prominent evident of action of enzyme on biomass. Further, the H. volcanii katG overexpression strains shows zone of clearance for malachite green azo dye. Thus, the crude peroxidase enzyme extracted from the cloned and transformed peroxidase gene of Haloferax volcanii can be utilized for enzyme pre-treatment for lignocellulosic biomass and aids in the saccharification and fermentation of biomass for biofuel production.